The present invention relates to tubular prostheses such as grafts and endoluminal prostheses including, for example, stent-grafts and aneurysm exclusion devices, and methods for placement of such grafts and endoluminal structures. Further, the present invention relates to a stent graft and deployment method.
A wide range of medical treatments have been previously developed using xe2x80x9cendoluminal prostheses,xe2x80x9d which terms are herein intended to mean medical devices which are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring or artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries such as those located within coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes. Various types of endoluminal prostheses have also been developed, each providing a uniquely beneficial structure to modify the mechanics of the targeted luminal wall.
A number of vascular devices have been developed for replacing, supplementing or excluding portions of blood vessels. These vascular grafts may include but are not limited to endoluminal vascular prostheses and stent grafts, for example, aneurysm exclusion devices such as abdominal aortic aneurysm (xe2x80x9cAAAxe2x80x9d) devices that are used to exclude aneurysms and provide a prosthetic lumen for the flow of blood.
One very significant use for endoluminal or vascular prostheses is in treating aneurysms. Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease or a genetic predisposition, which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aneurysms occurring in the abdominal aorta. Typically an abdominal aneurysm will begin below the renal arteries and may extend into one or both of the iliac arteries.
Aneurysms, especially abdominal aortic aneurysms, have been treated in open surgery procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique in view of the alternative of a fatal ruptured abdominal aortic aneurysm, the open surgical technique suffers from a number of disadvantages. The surgical procedure is complex and requires long hospital stays due to serious complications and long recovery times and has high mortality rates. In order to reduce the mortality rates, complications and duration of hospital stays, less invasive devices and techniques have been developed. The improved devices include tubular prostheses that provide a lumen or lumens for blood flow while excluding blood flow to the aneurysm site. They are introduced into the blood vessel using a catheter in a less or minimally invasive technique. Although frequently referred to as stent-grafts, these devices differ from covered stents in that they are not used to mechanically prop open natural blood vessels. Rather, they are used to secure an artificial lumen in a sealing engagement with the vessel wall without further opening the natural blood vessel that is already abnormally dilated.
Typically these endoluminal prostheses or stent grafts are constructed of graft materials such as woven polymer materials (e.g., Dacron,) or polytetrafluoroethylene (xe2x80x9cPTFExe2x80x9d) and a support structure. The stent-grafts typically have graft material secured onto the inner diameter or outer diameter of a support structure that supports the graft material and/or holds it in place against a luminal wall. The prostheses are typically secured to a vessel wall above and below the aneurysm site with at least one attached expandable annular spring member that provides sufficient radial force so that the prosthesis engages the inner lumen wall of the body lumen to seal the prosthetic lumen from the aneurysm
Abdominal Aortic Aneurysms are frequently treated with bifurcated devices that provide an artificial lumen for flow of blood past the aneurysm and into the iliac vessels that branch off from the aorta. One such commonly used device comprises a bifurcated device having one branch portion longer than the other branch portion. This enables deployment of the main body through one of the iliac arteries where the longer branch is deployed. An extension leg is then deployed through the second iliac artery and is connected with the shorter branch portion.
Iliac vessels associated with abdominal aneurysms frequently have tortuous and twisted anatomies and other structural abnormalities that can prevent effect introduction of an extension leg through an iliac vessel. Often it must be decided prior to deployment whether to use a single lumen prosthesis through one iliac vessel and join the vessels with a shunt further down in the anatomy, or to use a bifurcated prosthesis with an extension. Often a surgeon may not be able to determine the appropriate course of action until the prosthesis is in place or after attempts have been made to deploy an extension graft through a tortuous iliac artery. It would be desirable to provide a device that would enable the decision to be made during the deployment procedure. Devices have been proposed in U.S. Pat. No. 6,102,938, incorporated herein by reference, that provide for sealing off a bifurcated portion of a bifurcated AAA device before or after deployment. Such device is designed for situations where a determination is made during a procedure that it would not be possible to introduce an extension leg into the shorter bifurcated portion to provide blood flow through one of the iliac vessels. It would be desirable to provide an improved or alternative device for accomplishing such task.
Frequently, the AAA procedures are performed in emergency situations where the aorta has ruptured or is extremely fragile and about to rupture. In these situations, frequently a single leg device is deployed through the aorta and one of the iliac vessels occluding the second iliac vessel. This may be done because of the importance of reestablishing blood flow through the aorta and iliac vessel and stopping the loss of blood through the ruptured or rupturing vessel. Such situations may not permit deployment of the second (extension) leg. During this crucial time, in using an existing bifurcated device, blood would be able to flow through the shorter bifurcated portion of the prosthesis into the area of the aneurysm. Accordingly it would be desirable to provide an improved or alternative device that allows for deployment of a bifurcated device in emergency situations that would prevent further blood flow into the area of the aneurysm.
Accordingly one embodiment according to the present invention provides a novel device and method that include providing a bifurcated device with one leg initially in an occluded position preventing flow of blood through that portion into the aorta. Once the implant is in place and blood is excluded from the aneurysm site, an extension may be introduced and the occluded side opened to blood flow through the extension.
An embodiment of the endoluminal prosthesis comprises a bifurcated tubular member constructed of a graft material and at least one annular support member. The tubular graft is formed of a woven fiber for conducting fluid. The tubular member includes, a proximal opening and distal openings though the bifurcated portions providing a lumen or lumens through which body fluids may flow. When deployed, annular support members support the tubular graft and/or maintain the lumen in a conformed, sealing arrangement with the inner wall of a body lumen. One of the bifurcated portions is provided with a valve that can open or close to permit or prevent the flow of blood through the bifurcated portion. Various embodiments of the valve includes a member that move a section of graft or other material over or away from the opening into the short iliac leg of the bifurcated prosthesis to close or open the short leg to the flow of blood.
The annular support members of an embodiment of the prosthesis each comprise an annular expandable member formed by a series of connected compressible diamond structures. Alternatively, the expandable member may be formed of an undulating or sinusoidal patterned wire ring or other compressible spring member. Preferably the annular support members are radially compressible springs biased in a radially outward direction, which when released, bias the prosthesis into conforming fixed engagement with an interior surface of the vessel. Annular support members are used to create a seal between the prosthesis and the inner wall of a body lumen as well as to support the tubular graft structure. The annular springs are preferably constructed of Nitinol. Examples of such annular support structures are described, for example, in U.S. Pat. Nos. 5,713,917 and 5,824,041 incorporated herein by reference. When used in an aneurysm exclusion device, the support structures have sufficient radial spring force and flexibility to conformingly engage the prosthesis with the body lumen inner wall, to avoid excessive leakage, and prevent pressurization of the aneurysm, i.e., to provide a leak resistant seal. Although some leakage of blood or other body fluid may occur into the aneurysm isolated by the prosthesis, an optimal seal will reduce the chances of aneurysm pressurization and resulting rupture.
The annular support members are attached or mechanically coupled to the graft material along the tubular graft by various means, such as, for example, by stitching onto either the inside or outside of the tubular graft.
An embodiment according to the present invention provides such a tubular graft for endoluminal placement within a blood vessel for the treatment of abdominal and other aneurysms. In this embodiment, the endoluminal prosthesis is an aneurysm exclusion device forming a lumen for the flow of body fluids excluding the flow at the aneurysm site. The aneurysm exclusion device may be used for example, to exclude an aneurysm in the aorta (Abdominal Aortic Aneurysm (xe2x80x9cAAAxe2x80x9d) device) in which the prosthesis is bifurcated.
The generally Y-shaped bifurcated tubular prosthesis has a trunk joining at a graft junction with a pair of lateral limbs, namely an ipsilateral limb and a contralateral limb. In a bifurcated prosthesis, the proximal portion of the prosthesis comprises a trunk with a proximal opening and the distal portion is branched into at least two branches with distal openings. Preferably the ipsilateral limb is longer so that when deployed, it extends into the common iliac. The contralateral limb includes a valve located therein that is initially in a closed position in which body fluids flow from the proximal opening through the distal opening of the ipsalateral limb while the flow of body fluid through the contralateral limb is prevented by the valve. A single limb extension member is provided having a mating portion for coupling with a lateral limb of a bifurcated member and an adjustable length portion extending along an axis from a distal end of the mating portion. The insertion of the limb extension into the contralateral portion of the main prosthesis opens the valve which is then in part maintained open by the extension limb, permitting blood flow from the proximal opening in the main prosthesis through the distal opening in the contralateral and extension limbs.
The valve in one embodiment comprises a plurality of support members coupled to a section of graft material. One of the support members is an annular member forming an opening for the flow of body fluids. A proximal support member is a semicircular member which has an closed position in which the section of graft material forms a cover over the opening formed by the annular member, and an open position in which the section of graft material is held is a position against the wall of the prosthesis so that the opening formed by the annular member is in fluid communication with the flow of body fluid through the prosthesis.
In another embodiment the valve comprises a plurality of annular support members coupled to a section of graft material where at least one of the annular support members is configured to be folded to form a semicircular member engaged to an inner circumference of the bifurcated prosthesis. When the valve is in an open position, the support members are in an open configuration whereby the annular members and a section of graft material form a lumen through which blood may flow. When the valve is in a closed position, one of the annular support members is folded to that the graft material attached to the folded annular member is drawn across the opening through the short leg in which the valve is located.
In another embodiment the valve comprises a graft material sewn in part on an inner circumference of the bifurcated prosthesis and forming a pocket when the valve is closed. A portion of an annular member is sewn on to at least a portion of the section of graft material not sewn on to the prosthesis. When the valve is in a closed position, the annular member holds section of the graft material in a position over the opening in the short leg of the prosthesis. The annular member in this position is across from the location where the opposite side of the section of graft material is sewn on to the prosthesis. When the valve is in a closed position, the annular member holds the pocket formed by the section of graft material closed. The annular member in this position is against the location where the section of graft material is sewn on to the prosthesis so that the opening in the short leg provides a lumen through which blood may flow from the proximal end of the prosthesis to the distal end of the short leg.
The compressed profile of the prosthesis, including the valve, is sufficiently low to allow the endoluminal graft to be placed into the vasculature using a low profile delivery catheter. The prosthesis can be placed within a diseased vessel via deployment means at the location of an aneurysm. Various means for deliver of the device through the vasculature to the site for deployment, are well known in the art and may be found for example is U.S. Pat. Nos. 5,713,917 and 5,824,041. In general, the endoluminal prosthesis is radially compressed and loaded in a catheter for delivery to the deployment site. The aneurysm site is located using an imaging technique such as fluoroscopy and is guided through a femoral iliac artery with the use of a guide wire to the aneurysm site. Once appropriately located, a sheath restraining the tubular graft may be retracted to release the annular springs to expand and attach or engage the tubular member to the inner wall of the body lumen. The iliac extension is also loaded into a catheter and is then located into the main body of the stent graft and within the iliac vessel and is placed through an opened valve where it is deployed. According to an embodiment, when deployed, the iliac has proximal annular springs which when located within the inner lumen of the main body hold or maintain the valve open. The distal portion of the extension extends into one of the iliac vessels.